Water-soluble polymers in water-in-oil (inverse) emulsion form, i.e., water-soluble polymer/water as the discrete phase of the emulsion, and hydrocarbon solvent as the continuous phase of the emulsion, have found great utility in water treatment and related industries. The utility of the inverse emulsions is in large measure due to their ability to supply high concentrations of high molecular weight water-soluble polymers in "liquid", free-flowing form. As is well known to those skilled in the art, high molecular weight water-soluble polyelectrolytes are very viscous in solution, and concentrations in water above about 1% are extremely viscous and difficult to pour, pump, etc.
These inverse emulsion products generally comprise approximately equal quantities of hydrocarbon, polymer and water (about 30% of each), together with hydrophobic surfactants for stabilization of the emulsion and hydrophilic surfactants for subsequent inversion into water for use.
In order for these inverse emulsions to be used for various applications, including water-treatment, they generally must be activated by inversion of the emulsion, from a water-in-oil emulsion to an oil-in-water emulsion. This is generally done by diluting the emulsion with water. The self-inverting characteristics of the emulsions which contain the inverting surfactant thus allow the polymer to be "released" into the water, making the polymer available for use. By the same token, the oil phase becomes the discontinuous phase, and what is obtained when the emulsion is diluted with water is a hazy solution of the polymer in water, the haziness being the emulsified oil.
The inversion is generally conducted with sufficient quantities of water such that the polymer will be approximately at use concentration, usually about one percent polymer on an active basis, or less. Thus, one gram of emulsion containing about 30% polymer will require about 33 g of water in order to achieve a one percent solution. As is well known in the art, the polymers contained in the inverse emulsions are generally of high molecular weight, usually greater than one million up to about 20 million or more. For this reason, solutions of these high molecular weight polymers become very viscous above about one percent concentration in water, thus limiting their ability to be pumped, etc. Also for the aforementioned reasons, the inversion must be carefully conducted so that localized regions of high polymer concentration are avoided. Thus, the emulsion is always added to the well stirred aqueous portion.
One consequence of the self-inverting characteristics of the water-in-oil emulsions is that they are "unstable" in the presence of water. Thus, if a small amount of water is inadvertently introduced into the emulsion, the emulsion will invert in the area where the contaminating water is present. Since the polymer concentration in the localized area will tend to be very high, the inverted portion will have an extremely high viscosity, and may even be "gel" like. This results in an unusable portion of polymer which is also objectionable because it will tend to clog transfer lines, pumps, and the like.
The contamination of these emulsions with water is a common occurrence in manufacturing plants, shipping, and in use locations, and causes many problems in cleanup, filtration, and lost time. Such contamination can occur through spills, rain falling into open drums and tank trucks, and the like, and has resulted in increased surveillance on the part of personnel to avoid the possibility of contamination. It is thus well known that inverse emulsions of water-soluble polymers are incompatible with significant quantities of water, with the obvious exception of the dilution of the emulsions with such great quantities of water that the polymers will be at their practicable use concentrations (about 1% or less).
It is also known to those in the industry that combination treatments, in various applications, of these high molecular weight water-soluble polymers, in inverse emulsion form, with concentrated aqueous solutions of lower molecular weight polymers can be very useful. Because of the heretofore perceived inability of those skilled in the art to be able to combine the emulsions with the "destabilizing" aqueous solutions, these combination treatments have always been utilized as dual treatments, i.e., the polymers would be added in separate streams, from separate drums or tanks. In particular, many applications exist where high molecular weight cationic polymers in inverse emulsion form are used in combination with lower molecular weight cationic polymers in concentrated aqueous solution, via dual treatment systems.